/**
 * Storage封装
 */
 const  STORAGE_KEY = 'mall';
 export default{
   // 存储值
   setItem(key,value,module_name){
     if (module_name){
       let val = this.getItem(module_name);
       val[key] = value;
       this.setItem(module_name, val);
     }else{
       let val = this.getStorage();
       val[key] = value;
       window.sessionStorage.setItem(STORAGE_KEY, JSON.stringify(val));
     }
   },
   // 获取某一个模块下面的属性user下面的userName
   getItem(key,module_name){
     if (module_name){
       let val = this.getItem(module_name);
       if(val) return val[key];
     }
     return this.getStorage()[key];
   },
   getStorage(){
     return JSON.parse(window.sessionStorage.getItem(STORAGE_KEY) || '{}');
   },
   clear(key, module_name){
     let val = this.getStorage();
     if (module_name){
       if (!val[module_name])return;
       delete val[module_name][key];
     }else{
       delete val[key];
     }
     window.sessionStorage.setItem(STORAGE_KEY, JSON.stringify(val));
   }
 }